Although it is well established that hepatic macrophages play a crucial role in the development of liver fibrosis, the underlying mechanisms remain largely elusive. Moreover, it is not known whether other mononuclear phagocytes such as dendritic cells contribute to hepatic stellate cell (HSC) activation and liver fibrosis. Here we show for the first time that hepatic macrophages enhance myofibroblast survival in an NF-κB-dependent manner, and thereby promote liver fibrosis. Microarray and pathway analysis revealed no induction of HSC activation pathways by hepatic macrophages but a profound activation of the nuclear factor-kappa B (NF-κB) pathway in HSCs. Conversely, depletion of mononuclear phagocytes during fibrogenesis in vivo resulted in suppressed NF-κB activation in HSCs. Macrophage-induced activation of NF-κB in HSC in vitro and in vivo was mediated by IL-1 and TNF. Notably, IL-1 and TNF did not promote HSC activation but promoted survival of activated HSC in vitro and in vivo and thereby increased liver fibrosis, as demonstrated by neutralization in co-culture experiments, and genetic ablation of IL-1 and TNF receptor in vivo. Co-culture and in vivo ablation experiments revealed only a minor contribution to NF-κB activation in HSCs by dendritic cells, and no contribution of dendritic cells to liver fibrosis development, respectively. Conclusion Promotion of NF-κB-dependent myofibroblast survival by macrophages but not dendritic cells provides a novel link between inflammation and fibrosis.

Malignant melanoma is a type of very dangerous skin cancer. Histone modifiers usually become dysregulated during the process of carcinoma development, thus there is potential for a histone modifier inhibitor as a useful drug for cancer therapy. There is a multitude of evidence regarding the role of G9a, a histone methyltransferase (HMTase), in tumorigenesis. In this study, we first showed that G9a was significantly upregulated in melanoma patients. Using the TCGA database, we found a significantly higher expression of G9a in primary melanoma samples (n = 461) compared to normal skin samples (n = 551). Next, we knocked down G9a in human M14 and A375 melanoma cell lines in vitro via small interfering RNA (siRNA). This resulted in a significant decrease in cell viability, migration and invasion, and an increase in cell apoptosis. UNC0642 is a small molecule inhibitor of G9a that demonstrates minimal cell toxicity and good in vivo pharmacokinetic characteristics. We investigated the role of UNC0642 in melanoma cells, and detected its anti-cancer effects in vitro and in vivo. Next, we treated cells with UNC0642, and observed a significant decrease in cell viability in M14 and A375 cell lines. Furthermore, treatment with UNC0642 resulted in increased apoptosis. In immunocompetent mice bearing A375 engrafts, treatment with UNC0642 inhibited tumor growth. Results of Western blot analysis revealed that administration of UNC0642 or silencing of G9a expression by siRNA reduced Notch1 expression significantly and decreased the level of Hes1 in A375. All in all, the data from our study demonstrates potential of G9a as a therapeutic target in the treatment of melanoma.

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